A novel micro-CT analysis for evaluating the regenerative potential of bone augmentation xenografts in rabbit calvarias

Guided Bone Regeneration is a common procedure, yet, as new grafting materials are being introduced into the market, a reliable evaluation method is required. Critical size defect in animal models provides an accurate simulation, followed by histological sections to evaluate the new bone formation. However, histology is destructive, two-dimensional and technique-sensitive. In this study we developed a novel volumetric Micro-CT analysis to quantify new bone formation characteristics. Eight adult female New Zealand white rabbits were subjected to calvarial critical-size defects. Four 8 mm in diameter circular defects were preformed in each animal, to allow random allocation of four treatment modalities. All calvarias were scanned using Micro-CT. Each defect was segmented into four equal parts: pristine bone, outer, middle, and inner. Amira software (v. 6.3, www.fei.com ) was used to calculate the new bone volume in each region and compare it to that of the pristine bone. All grafting materials demonstrated that new bone formation decreased as it moved inward. Only the inner region differed across grafting materials (p = 0.001). The new Micro-CT analysis allowed us to divide each defect into 3D regions providing better understanding of the bone formation process. Amongst the various advantages of the Micro-CT, it enables us to quantify the graft materials and the newly formed bone independently, and to describe the defect morphology in 3D (bi- vs. uni-cortical defects). Providing an insight into the inner region of the defect can better predict the regenerative potential of the bone augmentation graft material. Therefore, the suggested Micro-CT analysis is beneficial for further developing of clinical approaches.

Screw-Type Collar vs. Non-Screw-Type Collar Implants—Comparison of Initial Stability, Soft Tissue Adaptation, and Early Marginal Bone Loss—A Preclinical Study in the Dog

Simple Summary

Implant neck characteristics may affect initial implant stability, soft tissue healing, and early marginal bone loss (EMBL) at second-stage surgery. Screw-type rough-surface collar implants had statistically significant poorer soft tissue healing and increased marginal bone loss compared to non-screw type implants at the time of 2nd-stage surgery. The significance of the novel implant design results in preventing EMBL awaits further research.

Abstract

Background: Implant neck characteristics may affect initial implant stability, soft tissue healing, and early marginal bone loss (EMBL) at second-stage surgery. The null hypothesis was that, following two-stage implant insertion, rough surface, non-screw-type collar implants will present lower EMBL at 2nd-stage surgery than rough-surface, screw-type collar implants. Methods: The study comprised seven male beagle dogs (mean weight 10.57 ± 2.8 kg; range 9–17 kg). A novel implant design was developed, composed of 2 parts: an apical part resembling a regular threaded implant, and a coronal non-screw-type collar, 4.2 mm long, served as the study group, whereas standard threaded implants served as control. Twenty-eight implants were placed: two on each side of the mandible. All implants were sand-blasted/acid-etched and of similar dimensions. Each dog received four implants. To assess location (anterior vs. posterior) impact on the outcomes, implants were placed as follows: group I—posterior mandible right—non-screw-type collar implants; group II—anterior mandible right—similar non-screw-type collar implants. To assess the collar-design effect on the outcomes, implants were placed as follows—Group III—anterior mandible left—control group, screw-type collar implants; Group IV—study group, posterior mandible left—non-screw-type collar implants. The following parameters were measured and recorded: insertion torque, soft tissue healing, early implant failure, and EMBL at 2nd-stage surgery. Results: No statistically significant differences were noted between groups I and II regarding all outcome parameters. At the same time, although insertion torque (55 N/cm) and early implant failure (0) were similar between groups III and IV, group III presented significantly poorer soft tissue healing (1.43 vs. 0.14) and increased marginal bone loss (0.86 vs. 0 mm). Conclusions: When a two-stage implant protocol was used, rough-surface non-screw-type collar implants led to superior outcomes at 2nd-stage surgery. Implant location did not affect the results. The significance of this result in preventing EMBL awaits further research.

Positive relationship between the dimensions of clinical gingival recessions and associated alveolar bone dehiscences: a biometric study

OBJECTIVES

To analyze the relationships between the dimension of clinical gingival recession and of the actual bone dehiscence.

METHOD AND MATERIALS

Data included measurements taken before and during root coverage surgical procedures. General health, smoking status, previous orthodontic treatment, probing depth, clinical measurements taken on gingival recessions, and the exposed alveolar bone dehiscences were recorded. Data were analyzed using descriptive statistics and linear regression model.

RESULTS

Twenty-three patient files were available. The mean age was 31.3 ± 12.1 years (range 13 to 51 years). Eight patients had previous orthodontic treatment. Incisor, canine, and premolar recessions amounted to 9, 8, and 6 teeth, respectively. The deepest recession per patient was recorded. The mean alveolar bone dehiscence depth was 6.78 ± 1.2 mm (range 5 to 9 mm). Patient-related or systemic findings, preceding orthodontic treatment, and tooth type were not correlated with alveolar bone dehiscence dimensions. A significant association was found between clinical recession and the alveolar bone dehiscence depths (P < .001, Fisher exact test). On average, each 1 mm increase in clinical recession depth involved an increase of 1.45 mm in alveolar bone dehiscence depth (P < .001, linear regression). The ratio between the clinical recession depth and width was significantly associated with the depth of the bone dehiscence (P = .007, Fisher exact test).

CONCLUSION

Within the limitations of the size of this study, clinical recession depth and width dimensions may help to predict the underling bone dehiscence magnitude. Gingival recession is associated with deformities of the underlying alveolar bone; this may be revealed during mucogingival procedures associated with full-thickness flaps. The association between the two may be of particular value to the operator as it may significantly affect the outcome of treatment. Furthermore, this relationship is of utmost importance in minimally invasive procedures that avoid flap elevation. A significant association was found between the depth of the clinical gingival recession and that of alveolar bone dehiscence. In addition, the ratio between the clinical recession depth and width was significantly associated with the depth of the bone dehiscence. Clinical recession depth and width dimensions may serve as an assessment predictor for the underling bone dehiscence magnitude.

The Incidence and Nature of Claims against Dentists Related to Periodontal Treatment in Israel during the Years 2005-2019

BACKGROUND

In recent years, worldwide dental malpractice claims have dramatically increased. The purpose of the present study is to analyze periodontal therapy related claims in Israel that led to legal decisions.

METHODS

This retrospective cohort study includes malpractice claims against dental practitioners related to periodontology between 2005 and 2019. Only closed cases where a final decision was made were included. The chi-square test or Fisher exact test for categorical variables were performed and a p value of <0.05 was considered statistically significant.

RESULTS

During the study period there were 508 legal claims related to periodontal disease. Most plaintiffs were women (63.4%), and 71.3% of the patients were >35 years old. Most claims (82.8%) were settled out of court and ended in compromise. Claims concerning the treatment of periodontal disease by periodontists accounted only for 4.5% (23/508) of the cases while 95.5% (485/508) of the claims were for complications secondary to another treatment. Prosthodontic treatment was involved with the highest number 54.5%, followed by dental implants 17.7%, and endodontics 11.6%. The allegations were related to pain and distress (84.8%), aggravation of existent periodontal disease (83.3%), tooth loss (78.1%), and violation of autonomy (47%).

CONCLUSIONS

The main cause for lawsuits was related to aggravation of periodontal disease during prosthetic or implant therapy and related to suspected faulty or inexistent preoperative diagnosis and planning.

PRACTICAL IMPLICATIONS

Periodontal consultation before dental treatment may reduce malpractice risks, adverse events, and un-necessary changes of treatment plans.

Effects of peri-implant infection on serum biochemical analysis

BACKGROUND

Peri-implant disease (PID) has not been directly linked to pathological organ changes. The present study assessed the dynamics of serum biochemical parameters in a model of experimental peri-implantitis in dogs, followed by open flap debridement.

METHODS

Seven male beagle dogs comprised the study group. Procedures were performed as follows-extractions of two premolars and one molar on each mandibular quadrant (Day 0); bone healing time (week14); placement of four rough-surface endoosseous implants, two on each mandibular side; implant uncovering (week 28); induction of experimental peri-implantitis by the use of three ligatures (weeks 31, 34, 37) followed by open flap debridement (week 42). Serum biochemical analysis following each procedure was compared to baseline. Biochemical parameters were assigned into four subsets of variables-inflammation, renal function, liver function, and blood glucose. Wilcoxon paired tests were conducted in order to identify statistically significant differences between baseline data and values obtained after each procedure RESULTS: Following experimental peri-implantitis, the dynamics of renal parameters and blood glucose were minimal whereas statistically significant (P < 0.05) increases were noted for inflammatory (total protein and albumin concentrations) and hepatic (ALT, AST) parameters. A statistically significant (P < 0.05) decrease was only noted for total bilirubin. After open flap debridement, inflammatory (total protein and albumin concentrations) and hepatic (AST) parameters returned to baseline.

CONCLUSIONS

Within their limits, the present results indicate that: (a) PID affects inflammatory and hepatic serum biochemical parameters, and (b) following open flap debridement most of the values returned to baseline.

Peri-implant disease affects systemic complete blood count values-an experimental in vivo study

OBJECTIVES

To assess complete blood count (CBC) dynamics following ligature removal and open flap debridement in experimental peri-implantitis in dogs.

MATERIALS AND METHODS

Seven male beagle dogs were included in the study. Four rough-surface implants were placed pair-wise in both sides of the mandible 14 weeks after tooth extraction. Second stage surgery was performed after 14 weeks. Experimental peri-implantitis was initiated 3 weeks later by ligature placement around the healing caps thus facilitating plaque accumulation and inducing inflammation and destruction of peri-implant tissues. Ligature removal and open flap debridement were performed 11 weeks later. The CBC values were compared with baseline after each procedure. Wilcoxon paired tests were conducted in order to identify statistically significant differences between baseline data and values obtained after each procedure.

RESULTS

Following experimental peri-implantitis, statistically significant (p < 0.05) increases were noted for white blood cells-WBC (9.62 ± 4.34 vs. 6.48 ± 1.34 cells per microliter of blood × 1000), hemoglobin-Hb (15.25 ± 0.94 vs. 13.52 ± 1.46, grams per deciliter), red blood cells-RBC (7.26 ± 0.79 vs. 5.9 ± 0.61 cells per microliter of blood × 1000), mean corpuscular hemoglobin-MCH (23.64 ± 0.96 vs. 23.16 ± 0.83 picograms/cell), platelets-PLT (349.86 ± 51.05 vs. 277.57 ± 66 cells per microliter of blood × 1000), and mean corpuscular hemoglobin concentration-MCHC (35.83 ± 0.27 vs. 31.04 ± 0.48 grams per deciliter). A statistically significant (p < 0.05) decrease in values was noted only for after ligature removal and open flap debridement. Mean corpuscular volume-MCV values were significantly lower (65.99 ± 2.31 vs. 74.65 ± 2.85 femtoliter) following 1^st ligature. Values returned to baseline after open flap debridement.

CONCLUSIONS

Within its limits, the present data suggest that experimentally induced peri-implantitis affects CBC values. Following surgical treatment, CBC values returned to normal. Clinical relevance This is the first study suggesting possible relationships between peri-implantitis and CBC values. Future studies, confirming such correlation, may provide an insight into the importance of peri-implant maintenance and treatment to minimize supporting tissues disease and reduce systemic effects.

Allograft and Collagen Membrane Augmentation Procedures Preserve the Bone Level around Implants after Immediate Placement and Restoration

Background: Immediate implant placement and restoration (IPR), is a reliable treatment modality. Purpose: This historical prospective study evaluated the medium-term outcomes of hard tissue after IPR in the anterior maxilla with simultaneous hard tissue augmentation. Methods: Seventy-three patients treated with single-implant IPR in the anterior maxilla were followed for 1-8 years. Treatment involved, atraumatic extraction, immediate implant placement and abutment adaptation, followed by simultaneous augmentation with mineralized freeze-dried bone allograft (FDBA) particles to fill the gaps and restore the ridge. The surgical site was stabilized with a resorbable collagen membrane, followed by the connection of an acrylic provisional restoration. Results: All implants osseointegrated during the follow-up period (mean, 34 ± 22 months). Radiographic evaluation of the distance between the implant shoulder (IS) and crestal bone level (CBL) was of 0.86 ± 0.86 mm and 0.8 ± 0.84 mm mesially and distally, respectively. Splitting the results into up to 3 years and 3-8 years of follow-up data, the corresponding values were 0.90 ± 0.83 and 0.68 ± 0.88 for the mesial aspect and 0.99 ± 0.87and 0.74 ± 0.83 for the distal aspect, respectively. Mean peri-implant probing depth was 3.63 mm (SD ± 1.06) and 16 implants (22%) presented at least one bleeding pocket of ≥5 mm (peri implant mucositis). Conclusions: The immediate replacement of a single maxillary tooth by implants combined with guided bone regeneration is a predictable treatment modality with favorable peri-implant bony response.

Sinus augmentation analysis of the gradient of graft consolidation: a split-mouth histomorphometric study

OBJECTIVE

The aim of this study was to histomorphometrically test the hypothesis that graft consolidation originates from the sinus floor.

MATERIALS AND METHODS

This prospective, randomized split-mouth study investigated patients undergoing bilateral maxillary lateral sinus floor augmentation using either freeze-dried bone allografts (FDBAs) or biphasic calcium phosphate (BCP) bone substitute. Apico-coronal core biopsies were harvested during implant placement 9 months after sinus floor augmentation, processed for histological observation, and measured histomorphometrically.

RESULTS

Biopsies were taken from 26 bilateral sites in 13 patients. The density of new bone (NB) decreased with increasing distance from the sinus floor. The percentage mean surface of NB ranged from 31 ± 9.5% at 2 mm from the sinus floor (G1) to 27.7 ± 11.2% at 4 mm (G2) for the FDBA specimens and from 30.0 ± 11.0% at G1 to 23.5 ± 9.9% at G2 for the BCP specimens. Evaluation of the residual graft particle (GP) area alone as a function of distance from the floor revealed a clear inverse gradient of 7.1 ± 6.6 to 9.1 ± 10.3 between G1 and G2 for the FDBA allografts, with the same tendency for the BCP alloplasts (21.9 ± 9.9 to 27.7 ± 6.6, respectively).

CONCLUSION

Our results support the concept that osteogenesis initiates in regions proximal to the bony walls of the maxillary sinus and may be enhanced by them.

CLINICAL RELEVANCE

The nature of the grafting material had a greater influence on the degree of NB formation in regions distant from the native walls where there is reduced inherent osteogenic potential.

Direct Contact Test for Evaluating Bacterial Growth on Machined and Rough Surface Implants: An In Vitro Study

OBJECTIVE

To use a modified direct contact test (DCT) to evaluate the bacterial growth on 3 commercially available implants.

MATERIALS AND METHODS

Streptococcus salivarius growth was tested on 1 machined surface and 2 commercial rough surface implants. Seven implants from each group were fixed to the cover of a 96-well microtiter plate. Bacterial suspension was placed on each implant, and the plate was incubated at 37°C for 1 hour to allow the suspension fluid to evaporate. Fresh medium was added to 7 corresponding wells in the microtiter plate, and the cover holding the implants was placed on the plate to enable immersion of the implant. Noncontaminated implant samples served as control. Bacterial growth was monitored spectrophotometrically at 650 nm for 24 hours.

RESULTS

There was a significant S. salivarius growth in all groups of test implants compared with the control. There was no significant difference between bacterial growth kinetics on treated and nontreated implant surfaces (P = 0.241).

CONCLUSION

Using the DCT, we found no difference in bacterial growth between machined and rough surface implants.

Comparison between mineralized cancellous bone allograft and an alloplast material for sinus augmentation: A split mouth histomorphometric study

BACKGROUND

Several grafting materials have been used in sinus augmentation procedures including autogenous bone, demineralized freeze-dried bone, hydroxyapatite, β-tricalcium phosphate, anorganic deproteinized bovine bone, and combination of these and others. Yet, the issue of the optimal graft material for sinus floor augmentation is controversial.

PURPOSE

This prospective, randomized split-mouth study was undertaken to histomorphometrically compare a biphasic calcium phosphate (BCP) alloplastic bone substitute and a human bone mineral allograft (freeze-dried bone allograft, FDBA) in patients undergoing bilateral maxillary lateral sinus floor augmentation.

MATERIAL AND METHODS

Apico-coronal core biopsies were harvested at 9 months from 26 bilateral sites in 13 treated patients. Specimens were processed for histological and histomorphometrical analyses.

RESULTS

Newly formed bone (NB) was evident in all specimens with values of 27.5% and 24.0% at the FDBA and BCP sites, respectively (P = .331). The residual graft particle values were 12.5% and 25.4% (P = .001), and the connective tissue values were 60.0% and 50.6%, respectively. The osteoconductive value was 52.6% for the FDBA and 26.7% for the alloplast (P = .001). The values for the measured residual graft particles, connective tissue, and osteoconductivity, but not for NB, showed highly significant differences between the two groups. All sections in the alloplast material showed evidence of a light chronic inflammatory infiltrate, mainly comprising lymphocytes and multinucleated giant cells.

CONCLUSIONS

Both graft materials are suitable for sinus floor augmentation, with the allograft material being more osteoconductive.

Temperature changes of one-piece implants during the setting of acrylic resin temporary crown. The effect of implant diameter. An in vitro study

The purpose of this work is to evaluate changes in temperature of one-piece titanium implant surface during the setting of acrylic resin temporary crowns and to correlate thermal changes to implant diameter. Thirty-three one-piece implants (ARRP, Alpha-Biotec) were divided into 3 groups according to diameter size (G1=3 mm, G2=3.3 mm, G3=3.6 mm). Implants were mounted on an acrylic glass apparatus. Thermocouples were positioned at the most coronal thread. Lower incisor temporary polycarbonate crowns were filled with 80 μL of self-curing acrylic resin and positioned immediately on the implant abutment. Thermal changes of the implant surface were recorded continuously for 10 min. Data were statistically analyzed using one-way analysis of variance. The mean initial temperature (C0) of groups G1, G2 and G3 was similar (24.79±0.78ºC, 25.26±0.63ºC, 24.97±1.06ºC, respectively). The setting of the acrylic resin temporary crown resulted in a significant increase in the implant surface temperature of all groups. The mean thermal amplitude (ΔC) for groups G1, G2 and G3 were 6.79±1.02ºC, 6.61±0.94ºC, 6.65±1.26ºC, respectively. The mean time to maximum temperature (Tmax) for groups G1, G2 and G3 were 337.38±42.91 sec, 324.69±41.46 sec and 317.98±37.91 sec respectively (P>0.05). Direct application of auto-polymerizing resin to the titanium abutment of one-piece implants significantly increased the cervical implant surface temperature. Implant diameter did not influence the temperature changes.

Bone-to-Implant Contact and New Bone Formation Within Human Freeze-Dried Bone Blocks Grafted Over Rabbit Calvaria

PURPOSE

To assess the extent of osseointegration with rough-surface implants and new bone formation (NBF) within human freeze-dried bone blocks (h-FDB) grafted over rabbit calvaria.

MATERIALS AND METHODS

A total of 18 rectangular h-FDB blocks were stabilized bilaterally to the calvaria of nine New Zealand rabbits by two mini titanium screws each. A total of 18 rough-surface implants (5.0 × 6.0-mm) were placed, 9 simultaneously (immediate placement [IP]) on one side and 9 at 3 months after block grafting (delayed placement [DP]) on the contralateral side. At 12 weeks after the second surgical procedure, block biopsies were harvested and processed for histologic analysis. Morphometric measurements consisted of bone-to-implant contact (BIC) and the extent of NBF from the calvarial surface and outward into the block. A paired t test was applied for statistical analysis.

RESULTS

All h-FDB blocks were integrated, and the implants showed clinical stability. Histologically, the BIC was primarily between the apical end of the implants and the host rabbit calvaria. Bone growth between the implant threads was minimal and inconsistent among all animals. Morphometric measurements showed that the mean BIC of the IP and DP implants with the blocks was 10.50% ± 5.99% and 23.06% ± 9.58%, respectively (P < .001). NBF was observed primarily in the cancellous compartment of the block adjacent to the recipient calvarial bed. The extent of NBF into the block around the IP and DP implants was 9.95% ± 8.41% and 12.90% ± 11.07%, respectively (P = 0.2).

CONCLUSION

In this model, a significantly lower BIC was demonstrated when implants were placed simultaneously with h-FDB block grafting compared to those placed in a two-stage mode. However, both techniques showed limited osseointegration.

Esthetic Assessment of Implants Placed into Fresh Extraction Sockets for Single-Tooth Replacements Using a Flapless Approach

BACKGROUND

To validate the concept of immediate implant placement and nonfunctional loading for use in the esthetically sensitive anterior maxilla, clinical trials should ideally include objective esthetic criteria.

PURPOSE

This study analyzed procedural results as graded by the pink esthetic score and white esthetic score (PES/WES).

METHODS

Thirty-nine suitable patients (mean follow-up 44.82 ± 28 months) were evaluated.

RESULTS

Thirty-eight implants fulfilled stringent criteria for successful osseointegration: absence of peri-implant radiolucency, implant mobility, suppuration, and pain. The mean total PES/WES was 15.50 ± 2.67 (range: 10-20). The mean total PES of 7.92 ± 1.60 (range: 5-10) indicated favorable overall peri-implant soft-tissue conditions. Root convexity and texture (1.63 ± 0.54) and curvature of the facial mucosa (1.68 ± 0.47) and distal papilla (1.66 ± 0.48) had the highest mean values, whereas acceptable levels of facial tissue (1.53 ± 0.73) and mesial papilla (1.42 ± 0.64) were the most difficult to fully achieve. The mean mesial and distal bone loss at data collection was, was 1.19 ± 0.54 and 1.15 ± 0.51, respectively. Periodontal disease severity (advanced chronic and aggressive periodontitis) was significantly associated with a low total PES (p = .048).

CONCLUSIONS

Objective PES/WES assessment validated immediate anterior maxillary single-tooth replacement and restoration as being a successful and esthetically predictable treatment modality in sites where the buccal bone had been preserved during the extraction at 1 year of follow-up.

[Establishing adequate periimplant zone of keratinized mucosa to enhance periimplant health]

The presence of an adequate zone of keratinized mucosa (KM) for maintaining gingival health associated with natural teeth is usually described as the presence of 1-2 mm of attached gingiva (AG). Dental implants without KM measuring 2 mm or more, exposed to high levels of bacterial plaque, have shown higher scores of plaque accumulation, peri-implant 'mucosal inflammation', bleeding on probing, peri-implantitis, alveolar bone loss and recession. In a recent study the effects of KM width on peri-implant tissue health was assessed. Significant improvements in clinical and immunological parameters were noted after increasing KM width by the use of free gingival graft (FGG) surgery. A recent systematic review evaluated the efficacy of various techniques and biomaterials adopted in periimplant KM augmentation. Free gingival graft, connective tissue graft, acellular dermal matrix and collagen matrix were used for KM augmentation. Improvements in KM width were reported in all studies. A definitive conclusion could not be achieved owing to the lack of well-designed studies and appropriate methods of studying soft tissue. The establishment of universal surgical guidelines and measurement systems is imperative in the future. The present manuscript will describe the clinical use of FGG for establishing adequate periimplant zone of KM to enhance periimplant health.

Radiological and Biological Assessment of Immediately Restored Anterior Maxillary Implants Combined with GBR and Free Connective Tissue Graft

OBJECTIVES

Radiologic and biologic assessment of immediately restored Implants combined with guided bone regeneration (GBR) and free connective tissue graft.

METHODS

1-4 year retrospective study involving 34 patients treated with maxillary immediately restored anterior single-implants. Soft tissue dimensions, radiographic bone loss, and biological and prosthetic complications were assessed.

RESULTS

During the mean follow up period of 29 months the study group presented a mean mesial bone loss of 1.10 ± 0.39 mm (range: 0.5-2.4 mm), and mean distal bone loss of 1.19 ± 0.41 mm (range: 0.4-2.1 mm). Mean periimplant probing depth of 3.49 mm (SD ± 1.06) and 2.35 (SD ± 0.52) for the contralateral tooth (highly significant p < 0.001). Bleeding on probing was present in 29.4% of the examined implant supported crown sites and 10.4% of the contralateral teeth (p < 0.001).

CONCLUSIONS

Anterior maxillary single-tooth replacement, using GBR and connective tissue graft according to the concept of immediate implant placement, and non-functional restoration is an accepted treatment modality achieving favorable peri-implant soft tissue condition.

Differences in crestal bone-to-implant contact following an under-drilling compared to an over-drilling protocol. A study in the rabbit tibia

OBJECTIVES

The objective of this study is to compare bone-to-implant contact (BIC) between implants inserted at high torque due to under-drilling of the crestal bone to those inserted at low torque due to over-drilling of the crestal bone.

MATERIALS AND METHODS

Forty implants with diameters of 3.75 mm (group A) or 3.55 mm (group B) were inserted in the proximal tibiae of NZW rabbits in two separate surgeries on day 0 or 21. Osteotomy of the crestal bone was finalized with a 3.65-mm drill. In group A, implants were inserted at torque ≥35 Ncm (under-drilling) and in group B with torque <10 Ncm (over-drilling). Implants and their surrounding bone were retrieved on day 42, thus creating 3- and 6-week observation periods, processed for non-decalcified histology and stained with toluidine blue. Crestal BIC (c-BIC) and total BIC (t-BIC) were measured. Wilcoxon test was used to evaluate differences between groups.

RESULTS

Three weeks post-surgery, the mean c-BIC in group A was 16.3 ± 3.3 vs 31.5 ± 3.4 % in group B (P < 0.05). At 6 weeks, a similar trend was observed (group A: 28.7 ± 3.6 %; group B: 38.4 ± 4.9 %) (P > 0.05). No differences in t-BIC were noted at 3 weeks and at 6 weeks between the groups.

CONCLUSIONS

Insertion of implants with an over-drilling protocol of the crestal aspect of the osteotomy resulted in increased short-term crestal bone-to-implant contact.

CLINICAL RELEVANCE

Insertion of implants with a high torque following an under-drilling protocol, commonly used for immediate loading, may reduce crestal bone-to-implant contact at early healing stages.

Tetracycline impregnation affects degradation of porcine collagen matrix in healthy and diabetic rats

OBJECTIVES

The present study evaluated the degradation of collagen matrix (CM) immersed in tetracycline (TTC) or phosphate-buffered saline (PBS) in diabetic and normoglycemic rats.

MATERIALS AND METHODS

Diabetes was induced in 15 rats by systemic streptozotocin (STZ) (experimental); 15 healthy rats served as controls. One day before implantation 60 CM disks, 5 mm in diameter, were labeled with biotin: 30 were immersed in tetracycline (TTC) and 30 in PBS. One disk of each type was implanted subdermally in each rat. Animals were euthanized after 3 weeks, and tissue specimens containing the disks were prepared for histologic analysis. Horseradish peroxidase (HRP)-conjugated streptavidin was used to detect the remaining biotinylated collagen. Residual collagen area within the CM disks was analyzed and compared to baseline.

RESULTS

Diabetes significantly increased the CM degradation. Immersion of the CM disks in a 50-mg/mL TTC solution before implantation decreased its degradation both in diabetic and normoglycemic rats.

CONCLUSIONS

Diabetes significantly increases collagen matrix degradation; immersion of collagen matrix in TTC before implantation decreases its degradation in both diabetic and normoglycemic conditions.

CLINICAL RELEVANCE

Immersion of medical collagen devices in TTC may be an effective means to decrease their resorption rate and increase their effectiveness, especially in situations with increased degradation such as diabetes.

The Use of Tilted Implant for Posterior Atrophic Maxilla

PURPOSE

To retrospectively analyze the influence of implant inclination on marginal bone loss at freestanding implant-supported fixed partial prostheses (FPPs) over a medium-term period of functional loading.

MATERIALS AND METHODS

Twenty-nine partially edentulous patients with freestanding FPDs supported by two implants placed in a two-stage procedure comprised the study group. The anterior implant was placed axially, and the posterior tilted distally. Mesial or distal inclination of each implant was measured in relation to the vertical axis perpendicular to the occlusal plane. Average bone loss was compared between straight and tilted implants, smokers, and nonsmokers.

RESULTS

Mean angulation of the anterior axial-positioned implant was 3.45 degrees distally (range 0-8) and of the distal implants was 32.83 degrees distally (range 20-50 degrees). Average bone loss after 1, 3, and 5 years was 0.89 (SD = 0.73), 1.18 (SD = 0.74), and 1.50 (SD = 0.81), respectively, for axial implants, and 0.98 (SD = 0.69), 1.10 (SD = 0.60) and 1.50 (SD = 0.67) for tilted implants, with no significant correlation between implant angulation and bone loss. A significant correlation between implant angulation and annual bone loss was obtained for tilted implants only (r = 0.52, p = .004).Using Albrektsson criteria, the success rate was 89.6% (26 out of 29 implants) for straight and 93.1% (27 out of 29) for tilted implants.

CONCLUSION

The study demonstrates no effect of implant angulation on peri-implant bone loss in the posterior maxilla.

[Animal experimentation, animal welfare and scientific research]

Hundreds of thousands of laboratory animals are being used every year for scientific experiments held in Israel, mostly mice, rats, rabbits, guinea pigs, and a few sheep, cattle, pigs, cats, dogs, and even a few dozen monkeys. In addition to the animals sacrificed to promote scientific research, millions of animals slain every year for other purposes such as meat and fine leather fashion industries. While opening a front against all is an impossible and perhaps an unjustified task, the state of Israel enacted the Animal Welfare (Animal Experimentation) Law (1994). The law aims to regulate scientific animal experiments and to find the appropriate balance between the need to continue to perform animal experiments for the advancement of research and medicine, and at the same time to avoid unnecessary trials and minimize animal suffering. Among other issues the law deals with the phylogenetic scale according to which experimental animals should be selected, experiments for teaching and practicing, and experiments for the cosmetic industry. This article discusses bioethics considerations in animal experiments as well as the criticism on the scientific validity of such experiments. It further deals with the vitality of animal studies and the moral and legal obligation to prevent suffering from laboratory animals.

Combined osteotome-induced ridge expansion and guided bone regeneration simultaneous with implant placement: a biometric study

PURPOSE

To evaluate the long-term outcome of a single-step ridge expansion osteotome procedure and implant placement combined with guided bone regeneration in patients presenting narrow maxillary alveolar ridges.

MATERIALS AND METHODS

During the period 1999 to 2010, 41 patients aged 19 to 77 years (18 males; 23 females) suffering from partial or full edentulism associated with horizontal resorption of the maxillary ridges (2.5-5 mm) were treated using the combined ridge expansion and guided bone-regeneration techniques to obtain an improved bony base for implant placement. Implant survival, bone width measurements, clinical and radiologic implant success, and clinical complications were recorded and analyzed.

RESULTS

Achievement of primary stability of the implant was impossible at six sites; these were recorded as failures. In the remaining 35 patients, one hundred sixteen endosseous titanium implants were simultaneously placed. Follow-up time varied between 6 and 144 months (mean 52.4); of these, 36% were followed up for periods of time longer than 60 months. Implant diameter and lengths varied between 3.3 to 4.8 and 12 to 16 mm, respectively. In the 35 successful procedures (one hundred sixteen implants), the overall implant survival rate was 100%. An average gain in ridge width was 3.5 ± 0.93 (p < .0001) and an average enlargement of the buccal bone was 1.91 ± 0.6 (p < .0001). The mean vertical mesial bone loss was 1.81 mm ± 1.07 (ranging from 0.3 to 4.2 mm), and the mean vertical distal bone loss was 1.74 mm ± 1.12 (ranging from 0.4 to 4.5 mm). In eight patients (32%), at least one implant presented bone loss of ≥3 mm.

CONCLUSIONS

Within the limitations of this study, we suggest that the combined osteotome-induced ridge expansion and guided bone regeneration simultaneous with implant placement is a reliable procedure with reduced morbidity and may offer an alternative in suitable situations.

Histomorphometric analysis of maxillary sinus augmentation using an alloplast bone substitute

PURPOSE

To evaluate the regenerative potential of a fully synthesized homogenous hydroxyapatite:β-tricalcium phosphate 60:40 alloplast material in sinus lift procedures.

MATERIALS AND METHODS

Hydroxyapatite:β-tricalcium phosphate was used for sinus floor augmentation. After 9 months, 12 biopsies were taken from 12 patients. Routine histologic processing was performed and specimens were analyzed using a light microscope and a digital camera.

RESULTS

Histologic evaluation showed 26.4% newly formed bone, 27.3% residual graft material, and 46.3% bone marrow. The osteoconductive index was 33.5%.

CONCLUSIONS

Hydroxyapatite:β-tricalcium phosphate 60:40 alloplast material was found to be biocompatible and osteoconductive in maxillary sinus augmentation procedures.

Opposing effects of diabetes and tetracycline on the degradation of collagen membranes in rats

BACKGROUND

Increased collagenolytic activity, characteristic of uncontrolled diabetes, may compromise collagen membrane (CM) survival. Tetracycline (TCN) possesses anticollagenolytic properties and delays CM degradation in healthy animals. This study evaluates the degradation of TCN--immersed and -non-immersed CMs in rats with diabetes compared to those with normoglycemia.

METHODS

Diabetes was induced in 15 12-week-old male Wistar rats by injection of 65 mg/kg streptozotocin. The control group consisted of 15 rats with normoglycemia. Sixty bilayered CM disks were labeled before implantation with aminohexanoyl-biotin-N-hydroxy-succinimide ester, of which 30 were immersed in 50 mg/mL TCN solution (experimental) or phosphate-buffered saline (PBS) (control). In each animal, two disks (control and experimental) were implanted in two midsagittal calvarial defects in the parietal bone. Similar non-implanted disks served as baseline. After 3 weeks, animals were euthanized, and the calvaria and overlying soft tissues were processed for demineralized histologic analysis. Horseradish peroxidase-conjugated streptavidin was used to detect the biotinylated collagen. The area of residual collagen within the membrane disks was measured and analyzed with a digital image analysis system. Several slides from each specimen were also stained with hematoxylin and eosin. Statistical analysis consisted of paired and unpaired t tests.

RESULTS

The amount of residual collagen in PBS-immersed disks was lower in rats with diabetes compared to rats with normoglycemia (69% of baseline versus 93%, respectively, P <0.001). TCN immersion increased the amount of residual collagen contents in both diabetic (83% of baseline) and healthy (97.5% of baseline) animals (P <0.0001).

CONCLUSION

Diabetes increases CM degradation, whereas immersion in 50 mg/mL TCN solution before implantation presents an opposite effect.

Histomorphometric analysis of newly formed bone after bilateral maxillary sinus augmentation using two different osteoconductive materials and internal collagen membrane

Deproteinized bovine bone mineral (DBBM) and human freeze-dried bone allograft (FDBA) were compared in five patients undergoing bilateral maxillary sinus floor augmentation using DBBM on one side and FDBA on the contralateral side. After 9 months, core biopsy specimens were harvested. Mean newly formed bone values were 31.8% and 27.2% at FDBA and DBBM sites, respectively (P = .451); mean residual graft particle values were 21.5% and 24.2%, respectively (P = .619); and mean connective tissue values were 46.7% and 48.6%, respectively (P = .566). Within the limits of the present study, it is suggested that both graft materials are equally suitable for sinus augmentation.

Timing of implant placement and augmentation with bone replacement material: clinical assessment at 8 and 16 months

PURPOSE

The purpose of this study is to evaluate implants placed at different times of bone augmentation.

MATERIALS AND METHODS

Four implants were placed in seven dogs: one at a 6-month bovine mineral grafted site (6-month Bio-Oss® grafted site [6mBio]), one at a grafted membrane-protected simultaneously augmented (Fresh Bio-Oss® grafted site [FrBio]) site, one at a clotted (nongrafted clotted membrane-protected site [Clot]) membrane-protected site, and one at a pristine (nongrafted uncovered site [Cont]) site. Implants were exposed after 6 months. The same protocol was repeated on the contralateral side, at a delay of 8 months. Peri-implant care was performed throughout the hygienic phase (2 and 10 months, respectively) every 48 to 72 hours. Probing depth and bleeding on probing were recorded. Implant stability was determined by a Periotest® (Medizintechnik Gulden, Modautal, Germany). Statistical analysis was conducted using analysis of variance with repeated measures.

RESULTS

Average probing depth at the simultaneously grafted sites was 2.21 mm and 2.03 mm at 8 and 16 months, respectively. At the 6-month grafted sites, it was 1.96 mm and 1.57 mm. At the Clot sites, it was 2.68 mm and 2.07 mm, and 2.21 mm and 1.82 mm at the Cont sites, respectively. The average bleeding on probing was 0.50 and 0.42 at the FrBio sites, and 0.35 and 0.07 at the 6mBio sites during the respective periods. At the Clot sites, it was 0.50 and 0.28, and at the Cont sites, 0.43 and 0.21, respectively. Probing depth significantly reduced over the time at 6mBio, Clot, and Cont sites (p < .03). Average implant stability score at the FrBio sites was -0.24 and -0.27, and -0.50 and -0.46 at the 6mBio sites, at 8 and 16 months, respectively. At the Clot sites, it was -0.35 and -0.46. Cont sites averaged -0.37 at both periods. Implant stability was significantly higher (p < .005) comparing 6mBio over FrBio, 6mBio over Cont, and Clot over FrBio sites.

CONCLUSIONS

Immediate and delayed augmentations are safe modes. Probing depth and bleeding indices gradually improved along time. Implant stability was higher at the delayed mode.

Clinical and histomorphometric observations around dual acid-etched and calcium phosphate nanometer deposited-surface implants

PURPOSE

The objective of this study was to compare the clinical and histologic peri-implant parameters of a nano-calcium phosphate (CaP)-coated dual acid-etched (DAE) implant (n = 7) to those of an uncoated DAE implant (n = 7).

MATERIALS AND METHODS

The study included seven dogs who received implants bilaterally in edentulous mandibular areas; in the right side, procedures were performed 8 months after procedures in the left mandible. Clinical parameters were measured prior to euthanasia (8 months after the second set of implants was placed), followed by histologic nondecalcified processing for morphometric evaluation. Bone-implant contact (BIC), crestal bone resorption (CBR), intrabony defect (IBD), and bone area fraction (BAF) were measured. Analysis of variance with repeated measures and a two-tailed Pearson correlation test were applied.

RESULTS

Probing depth, Bleeding Index, and keratinized mucosal height were stable in both groups; there was a significant improvement in probing depths with time (P = .014). Morphometric measurements showed BIC from 75% to 89% in both groups at 8 and 16 months. The nano-CaP-coated group (n-CaP) showed a significant increase in BIC over time when compared to the DAE group (P = .02). Crestal bone level was maintained in both groups with average resorption of 1.4 to 1.5 mm at the n-CaP implants and 1.1 to 1.2 mm at the DAE implants at 8 and 16 months, respectively. Mean IBD values were 0.88 to 1.18 mm at the n-CaP implants and 0.65 to 0.66 mm at the DAE implants at the respective periods.

CONCLUSIONS

Within the limitations of this study, both the DAE and the n-CaP-surface implants showed successful osseointegration and functional soft and hard tissue adaptation. Except for the significant increase in BIC around the n-CaP implants over time, both showed similar clinical and histologic findings.

[Soft tissue grafts for the treatment of mucogingival deformities and conditions on edentulous ridges]

Soft tissue grafts are commonly used to restore and/or improve mucogingival deformities and conditions around teeth or on edentulous ridges. This include vertical and/or horizontal ridge deficiency, lack of gingiva/keratinized tissue, decreased vestibular depth and abnormal color. The present article describes and illustrates different procedures using autologous soft tissue grafts including masticatory mucosal free graft, masticatory mucosal pedicle graft, subepithelial free connective tissue graft, and subepithelial dermal graft. The functional and esthetic advantages and limitations of each graft for each condition are discussed.

[Buccal bony exostoses induced by free gingival grafts]

Buccal Bony Exostoses (BBE) is a local benign osseous overgrowth continuous with the facial aspect of the jaw. Post operative BBE may be the result of dermal grafts used to restore the buccal vestibulum, of connective tissue graft placement, and of Free Gingival Grafts (FGG) procedures. In 46 patients in whom 72 FGG procedures were performed by the senior author (HT) over the past 12 years, BBE was clinically and radiographically diagnosed. In one case the tumor was surgically removed. The etiology, pathogenesis and frequency of BBE following FGG procedures was reviewed and discussed. We suggest that the BBE may develop owing to periosteal surgical trauma during FGG procedures, and suggest that this phenomenon receives further attention.

Simultaneous versus two-stage implant placement and guided bone regeneration in the canine: histomorphometry at 8 and 16 months

AIM

To compare the effect of timing of implant placement and guided bone regeneration (GBR) procedure on osseointegration and newly formed bone at 8 and 16 months.

MATERIAL AND METHODS

In seven dogs, four different sites were bilaterally established: (1) an implant placed in a 6-month healed (6m-GBR) bovine bone mineral (BBM) grafted site; (2) a simultaneously placed implant with the grafted BBM (Si-GBR) followed by a membrane coverage; (3) an implant placed in a membrane-protected non-grafted defect; and (4) an implant placement in a naturally healed site (Cont). Histomorphometry was obtained at 8 and 16 months post-implant placement. Bone-implant contact (BIC), crestal bone resorption (CBR), vertical intra-bony (VIB) defect, bone (BAF) and particle (PAF) area fractions, and osteoconductivity (CON) levels were measured.

RESULTS

In all sites, BIC ranged between 62% and 79% with no significant differences. PAF ranged from 17% to 27%, with no effect of time. At 8 and 16 months, BAF was significantly smaller at the Si-GBR site when compared with all other sites, CON was significantly greater at the 6m-GBR site, and CBR and VIB were significantly smaller at the 6m-GBR when compared with the Si-GBR sites.

CONCLUSIONS

The simultaneous and delayed techniques both showed a similar osseointegration level over time. However, the staged approach showed enhanced newly formed bone, higher osteoconduction around the grafted mineral, less CBR, and smaller vertical bone defect over time compared with the combined approach.

Maxillary sinus augmentation by the crestal core elevation technique

BACKGROUND

The crestal core elevation (CCE) technique is reportedly a less invasive procedure than the lateral window elevation technique. We retrospectively evaluated long-term outcomes of CCE procedures over an 11-year time period.

METHODS

Core preparations were made after extractions of 57 upper molars in 45 patients. Extraction sites were drilled with a calibrated trephine bur to an estimated distance of 1 mm from the sinus membrane. The trephined interradicular bone and underlying sinus membrane were imploded into the sinus. The surgical crater and residual extraction socket were filled with deproteinized bovine bone mineral or freeze-dried bone allograft, stabilized, and protected with an absorbable collagen membrane and fully covered with coronally positioned flaps. Implants were placed 4 months later. Success was defined if ≥9 mm available bone height was available. Where the available bone height varied between 7 and 9 mm, implant placement was complemented using the bone-added osteotome sinus floor elevation technique; those sites were defined as a "partial success."

RESULTS

The CCE technique was successful in 31 (68.9%) out of 45 sites, and partially successful in six (13.3%) out of 45 sites. Eight sites failed (17.8%). Surgical failures were caused by core detachment resulting in large tears of the sinus membrane. Implants placed in successful sites presented a 100% survival rate during the study duration.

CONCLUSIONS

CCE implemented simultaneously with molar extractions provided therapeutic benefits and clinical limitations. The subsequent implant placement using CCE revealed an excellent survival rate in the study population evaluated.

Esthetic treatment of peripheral giant cell granuloma using a subepithelial connective tissue graft and a split-thickness pouch technique

BACKGROUND

Peripheral giant cell granuloma (PGCG) is a reactive hyperplastic lesion involving the gingiva or alveolar mucosa consisting of proliferating endothelial cells, a rich capillary bed, chronic inflammatory cells, fibroblasts, and giant cells. After complete clinical removal of PGCG recurrence occurs in about 10% of cases, and may result in an esthetic and functional soft tissue defect. This report describes a surgical procedure involving complete removal of a gingival PGCG in the maxillary esthetic zone and immediate tissue restoration achieving complete gingival augmentation.

METHODS

A 15-year-old female presented with a red, nodular, asymptomatic lesion, approximately 3.5 mm in diameter, located above the maxillary left lateral incisor. The lesion was excised down to the underlying root resulting in a 6 x 5-mm mucogingival dehiscence defect. Corrective surgery included a subepithelial connective tissue graft peripherally covered by the surrounding gingiva and stabilized by 5/0 resorbable sutures.

RESULTS

Healing was uneventful, resulting in healthy and esthetic gingiva. Microscopic examination of the biopsy specimen was consistent with the diagnosis of PGCG.

CONCLUSIONS

PGCG may follow an aggressive course, sometimes requiring preemptive surgical intervention. Grafting a subepithelial connective tissue graft peripherally covered by the surrounding gingiva, without raising a gingival flap, successfully eliminated the gingival defect. The free gingival margin of the neighboring teeth and the mucogingival junction remained unchanged.

Spontaneous pigmentation of non-pigmented palatal tissue after periodontal surgery

BACKGROUND

A 22-year-old African American female was referred for augmentation of keratinized gingiva around implants at the right and left maxillary second premolar sites. Presurgical evaluation revealed generalized melanosis of the buccal gingiva and a lack of keratinized tissue around implants at sites #4 and #13. No pigmentation was noted on the palatal tissues.

METHODS

Thick free gingival grafts were harvested bilaterally from the non-pigmented palate and secured to the recipient sites with bioabsorbable sutures. Hemostasis was achieved at the palatal donor sites with moistened gauze, and an acrylic stent was delivered for patient comfort.

RESULTS

Both palatal donor sites healed with spontaneous pigmentation. The pigmentation intensified with time but resulted in no adverse outcome.

CONCLUSIONS

Post-surgical healing in patients with gingival pigmentation is not entirely predictable, as multiple studies have demonstrated widely inconsistent results in regards to gingival pigmentation upon healing. When performing periodontal plastic surgery in patients with pigmented oral tissues, it is important to discuss all possible outcomes, including spontaneous pigmentation.

Bio-degradation of a resorbable collagen membrane (Bio-Gide) applied in a double-layer technique in rats

OBJECTIVE

The aim of this study was to evaluate histologically the bio-degradation of two layers of Bio-Gide((R)) (BG) membrane, as compared with that of a single layer.

MATERIAL AND METHODS

Two circular calvarial bony defects, 5 mm in diameter, were made in 24 Wistar rats. BG membrane, labeled with biotin, was cut into 5-mm-diameter disks, and placed in defects either as a mono-layer membrane (MLM) or as a double-layer membrane (DLM). Rats were sacrificed after 4 or 9 weeks and histology was performed. Membranes were stained with horseradish peroxidase-conjugated streptavidin and aminoethyl carbazole as a substrate for detection of biotinylated collagen. The area of collagen and thickness of the residual membranes were measured by image analysis software. Statistical analysis was performed using the non-parametric Wilcoxon's signed-ranks test.

RESULTS

At 4-week collagen area per measurement window within the DLM sites (0.09+/-0.05 mm(2)) was significantly greater (P<0.01) than that in the MLM sites (0.047+/-0.034 mm(2)). At 9 weeks, the collagen area was also greater in the DLM sites (0.037+/-0.026 mm(2)) compared with that of the MLM sites (0.025+/-0.016 mm(2)); however, this difference did not reach statistical significance. The rate of membrane degradation, calculated as percent membrane lost compared with baseline, was similar for the DLM and MLM at both time points ( approximately 60% at 4 weeks and approximately 80% at 9 weeks). In addition, the residual DLM thickness at 4 weeks (475.5+/-73.77 mum) was significantly (P<0.01) greater than that of MLM (262.38+/-48.01 mum). At 9 weeks, membrane thickness was also greater in the DLM sites (318.22+/-70.45 mum) compared with that of the MLM sites (183.32+/-26.72 mum); however, this difference did not reach statistical significance. The reduction in thickness between 4 and 9 weeks was 30% for MLM and 33% for DLM.

DISCUSSION

The use of a double layer of BG membrane results in a barrier of increased collagen area and thickness, compared with application of a single layer.

Effect of systemic tetracycline on the degradation of tetracycline-impregnated bilayered collagen membranes: an animal study

BACKGROUND

Premature collagen membrane degradation may compromise the outcome of osseous regenerative procedures. Tetracyclines (TTCs) inhibit the catalytic activities of human metalloproteinases. Preprocedural immersion of collagen membranes in TTC and systemic administration of TTC may be possible alternatives to reduce the biodegradation of native collagen membranes.

AIM

To evaluate the in vivo degradation of collagen membranes treated by combined TTC immersion and systemic administration.

MATERIALS AND METHODS

Seventy-eight bilayered porcine collagen membrane disks were divided into three groups and were immersed in 0, 50, or 100 mg/mL TTC solution. Three disks, one of each of the three groups, were implanted on the calvaria of each of 26 Wistar rats. Thirteen (study group) were administered with systemic TTC (10 mg/kg), while the remaining 13 received saline injections (control group). Calvarial tissues were retrieved after 3 weeks, and histological sections were analyzed by image analysis software.

RESULTS

Percentage of remaining collagen area within nonimpregnated membranes was 52.26 ± 20.67% in the study group, and 32.74 ± 13.81% in the control group. Immersion of membranes in 100 mg/mL TTC increased the amount of residual collagen to 63.46 ± 18.19% and 42.82 ± 12.99% (study and control groups, respectively). Immersion in 50 mg/mL TTC yielded maximal residual collagen values: 80.75 ± 14.86% and 59.15 ± 8.01% (study and control groups, respectively). Differences between the TTC concentrations, and between the control and the study groups were statistically significant.

CONCLUSIONS

Immersion of collagen membranes in TTC solution prior to their implantation and systemic administration of TTC significantly decreased the membranes' degradation.

Histomorphometric evaluation of natural mineral combined with a synthetic cell-binding peptide (P-15) in critical-size defects in the rat calvaria

PURPOSE

The objective of this study was to histomorphometrically evaluate the synthetic peptide analog P-15 bound to anorganic bovine mineral (Pepgen/P15) in critical-size defects in the rat calvaria.

MATERIALS AND METHODS

A 5-mm-diameter critical-size defect was prepared in 48 rat skulls and divided into 4 equal groups: Pepgen/P15 particles covered by a membrane, Pepgen/P15 particles uncovered, nongrafted membrane-protected sites, and nongrafted uncovered control sites. At 12 weeks, histomorphometric measurements were made of the percentage area of newly formed bone and residual particles, the length of internal and external bone bridging, and linearly, the regenerated marginal and central total tissue augmentation height.

RESULTS

Nongrafted, membrane-protected sites gained 60.6% of newly formed bone, followed by 50.6% and 44.2% (P < .05 versus membrane only) at the grafted covered and uncovered sites, respectively. All experimental sites contained significantly (P < .005) more bone than did control sites (19.9%). In both types of grafted sites, the percentage area of Pepgen/P15 particles was similar. Mean internal and external length of bone bridging at nongrafted membrane-protected sites (76.7% and 71.2%, respectively) was significantly greater (P < .005) than that of the grafted covered (43.95% and 51.8%, respectively), grafted uncovered (28.7% and 23.9%, respectively), and control (28% and 25.5%, respectively) groups, except for internal bone bridging in the grafted covered sites. Regenerated marginal and central augmentation heights (0.92 mm and 1.02 mm, respectively) were greatest in the grafted covered group, followed by the non-grafted membrane-protected (0.88 mm and 0.51 mm, respectively), and grafted uncovered (0.89 mm and 0.12 mm, respectively) groups, all of which were significantly greater (P < .001) than the control group (0.63 mm and 0.04 mm, respectively).

CONCLUSION

While anorganic bovine mineral/cell-binding peptide contributes in volume, membrane application significantly increases the amount of bone regeneration.

Biodegradation of three different collagen membranes in the rat calvarium: a comparative study

BACKGROUND

Collagen barrier membranes are commonly applied in periodontal and bone-regenerative procedures. Membranes differ in their resorption pattern following implantation, thus influencing clinical outcome. The purpose of this study was to quantitatively evaluate the biodegradation of three different commercially available collagen membranes.

METHODS

Collagen membranes were cut into 5-mm-diameter disks and labeled with aminohexanoyl-biotin-N-hydroxy-succinimide ester. One membrane disk of each type (non-cross-linked [NCL], glutaraldehyde cross-linked [GCL], and ribose cross-linked [RCL]) was implanted on the calvaria of 20 Wistar rats. Block sections were retrieved after 2 days (baseline, two animals), 14 days (10 animals), or 28 days (eight animals). Decalcified histologic sections were stained with streptavidin horseradish peroxidase. Residual membrane thickness and area were measured. Statistical analysis consisted of analysis of variance (ANOVA) with repeated measures.

RESULTS

Statistically significant differences in the amount of residual membrane material were recorded within each membrane (among different time points) and among different membranes at the same time points (P <0.001). At 28 days, the least amount of residual collagen area, expressed as the percentage of baseline, was observed in the NCL group (13.9% +/- 10.25%), followed by the GCL (24.7% +/- 35.11%) and RCL (91.3% +/- 10.35%) groups. Residual membrane thickness, expressed as the percentage of baseline thickness, presented a similar pattern (31% +/- 16.55%, 37% +/- 41.90%, and 94.1% +/- 12.22%, respectively). ANOVA with repeated measures showed a significant interaction between membranes and time (P <0.001).

CONCLUSIONS

The tested membranes differed in their degradation patterns and collagen contents. Membranes should be chosen for each clinical case according to the desired biodegradation characteristics.

Implant locating and placement based on a novel tactile imaging and registration concept: a technical note

Computed-assisted surgery (CAS) has been designed to improve oral implant planning and positioning and to increase safety and operator comfort. This is especially important in the esthetic zone, at sites with bone deficiency, and when minimally invasive implant placement is the therapy of choice. Current available CAS systems are relatively large and expensive and require a lengthy learning period. This report presents a novel tactile imaging and registration concept that enables the operation of a newly developed computerized implant locating system. An intraoral bone-sounding device maps the surface of the jaw through the soft tissue. Bone contour data are registered over the computerized tomographic image. Guided by treatment preplanning software, a chairside robotic manipulator fabricates guiding sleeves that direct the drill and implant during the osteotomy and implant placement, respectively. The authors' clinical experience shows that tactile registration based the Implant Locating System is simple to use and provides accurate implant design and placement that requires only basic computer experience, minimal operational space, and low infrastructure investment. The system allows final adjustments at the time of operation, transforming each implant surgery into a fully monitored procedure.

Severely resorbed mandible treated with iliac crest autogenous bone graft and dental implants: 17-year follow-up

Severe bone atrophy in the mandible may result in weakening of the jaw, unstable dentures, and dysfunction of the inferior alveolar nerve. These conditions were diagnosed in a 65-year-old woman who presented with a severely resorbed mandible. The interforaminal region of the mandible was augmented with an onlay graft harvested from the iliac crest. Four dental implants stabilized the graft by anchoring it inferiorly to the residual mandibular basal bone. Implants later served as abutments for a fixed 12-unit implant-supported prosthesis. The patient was followed for 17 years, during which the mandibular prosthesis was replaced twice. Despite the initial questionable prognosis, oral rehabilitation was successful, with no detectable clinical signs of bone loss over the 17-year follow-up period.